Bone spavin
Encyclopedia
Bone spavin is a bony growth within the lower hock
Hock (zoology)
The hock, or gambrel, is the joint between the tarsal bones and tibia of a digitigrade or unguligrade quadrupedal mammal, such as a horse, cat, or dog...

 joint of horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...

 or cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...

. It is caused by osteoarthritis
Osteoarthritis
Osteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion...

, and the degree of lameness
Lameness (equine)
Lameness in horses and other equidae is a term used to refer to any number of conditions where the animal fails to travel in a regular and sound manner on all four feet...

 that results can be serious enough to end a horse's competitive career.

Description of bone spavin

Bone spavin is osteoarthritis
Osteoarthritis
Osteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion...

, or the final phase of degenerative joint disease (DJD), in the lower three hock joints. It usually affects the two lowest joints of the hock (the tarsometatarsal and the distal intertarsal joints), with the third joint, the proximal intertarsal, being the least likely to develop bone spavin. This condition has more than one ‘type’. Jack spavin is the term used if the lesion on the tarsal and carpal bones is large. If the pathology occurs higher in the joint than is typical, it is termed high spavin. Conversely, occult spavin does not produce any significant exostoses on the small tarsals, whilst bog spavin
Bog spavin
Bog Spavin is a swelling of the tibiotarsal joint of the horse's hock which, in itself, does not cause lameness. The joint becomes distended by excess synovial fluid and/or thickened synovial tissue bringing about a soft, fluctuant swelling on the front of the joint, as well as in the medial and...

and blood spavin do not involve bony changes.

Cartilage compression

Excessive compression can cause, over time, the cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

 between the upper and lower surfaces of the lower tarsal bones to become compressed and eroded. The joint spaces then become smaller, and new bone growth may occur in the area.

Uneven loading

Uneven loading causes excessive compression of the cartilage and bone on one side, and strain in the joint capsule and supporting ligaments on the other side. When the joint is repeatedly overloaded on the edge of its surface, exostoses
Exostosis
An exostosis is the formation of new bone on the surface of a bone. Exostoses can cause chronic pain ranging from mild to debilitatingly severe, depending on where they are located and what shape they are....

, or "bone spurs," occur. Strain of the supporting ligaments can cause exostosis around the joint as well.

Contributing factors

There are several conformational defects that contribute to bone spavin. Those that cause uneven loading of the hocks, such as sickle hock
Sickle-hocked
Sickle-hocked is the technical term used to describe a specific type of incorrect leg structure in animals. The back leg joints of an animal, usually a horse or other equine mammal, are set with too much angle, resulting in the hock also being excessively angled. This can result in uneven hoof...

s and cow hock
Cow-hocked
Cow-hocked is the condition in a livestock animal where the back leg joints of the animal are set incorrectly. This term is used to describe when the back 'knee' on an animal is set inward, resulting in a splayed look in the back legs. This can result in the uneven wearing of hooves, which can end...

s, are especially noteworthy. Poor trimming or shoeing
Horseshoe
A horseshoe, is a fabricated product, normally made of metal, although sometimes made partially or wholly of modern synthetic materials, designed to protect a horse's hoof from wear and tear. Shoes are attached on the palmar surface of the hooves, usually nailed through the insensitive hoof wall...

 can also contribute to bone spavin in any horse, no matter what their conformation.

Certain types of activities may also contribute to uneven or repeated loading of the lower hock joints, and thus bone spavin. These include sports that require a great deal of hock flexion (dressage
Dressage
Dressage is a competitive equestrian sport, defined by the International Equestrian Federation as "the highest expression of horse training." Competitions are held at all levels from amateur to the World Equestrian Games...

), stress (jumping
Show jumping
Show jumping, also known as "stadium jumping," "open jumping," or "jumpers," is a member of a family of English riding equestrian events that also includes dressage, eventing, hunters, and equitation. Jumping classes commonly are seen at horse shows throughout the world, including the Olympics...

), sudden stops or turns (western events, such as reining
Reining
Reining is a western riding competition for horses where the riders guide the horses through a precise pattern of circles, spins, and stops. All work is done at the lope and gallop; the fastest of the horse gaits...

), or a great deal of concussion (Standardbred racing).

"Juvenile spavin" is the occurrence of bone spavin in horses less than 3 years old. It usually occurs before the animal has done much work. While osteochondrosis
Osteochondrosis
Osteochondrosis is a family of orthopedic diseases of the joint that occur in children and adolescents and in rapidly growing animals, particularly pigs, horses, and dogs. They are characterized by interruption of the blood supply of a bone, in particular to the epiphysis, followed by localized...

 lesions are the likely cause in some cases, this condition can also occur secondary to the distortion of the cuboidal bones which can occur in premature or dysmature foals.

Typical signs of bone spavin

Initially, signs of bone spavin may include sporadic and vague hindlimb lameness. Some horses may become uncomfortable in one lead, or may demonstrate stiffness walking downhill.

In many cases lameness worsens, becoming more obvious and consistent. Advanced cases may have a bony swelling on the hock, typically on the inside of the joint. Lameness, although usually worse in one leg, is commonly bilateral.

The affected limb usually lands toe-first, wearing down that foot faster than the other. The affected limb usually has a shorter, lower arc than the other foot, as the horse is trying to reduce the painful flexion of the joint, so the leg appears to drag.

A flexion test
Flexion test
A flexion test is a veterinary procedure performed on a horse, generally during a prepurchase or a lameness exam. The animal's leg is held in a flexed position for 30 seconds to up to 3 minutes , and then the horse is immediately trotted off and its gait is analyzed for abnormalities and uneveness...

 of an affected limb often produces a temporary worsening of the lameness. Such a response to a flexion test would support the diagnosis of bone spavin. A flexion test involves holding the hock in forced flexion
Flexion
In anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...

 for a period of time before trotting the horse away immediately.

Diagnosis of bone spavin

A provisional diagnosis of bone spavin should usually be supported by further investigation in order to confirm the diagnosis.

X-ray

Typical radiographic
Radiography
Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....

 changes include spurs, new bone, bone destruction and/or joint narrowing or loss.

Intra-articular local anaesthesia

Anaesthesia of an affected joint is a more definitive way of confirming the presence of pain arising from that joint. Introduction of local anaesthetic
Local anesthetic
A local anesthetic is a drug that causes reversible local anesthesia, generally for the aim of having local analgesic effect, that is, inducing absence of pain sensation, although other local senses are often affected as well...

 into a joint should abolish or at least significantly lessen the lameness. This technique is not absolutely specific, as the distal pouches of the tarsometatarsal joint are immediately adjacent to the suspensory ligament
Suspensory ligament
Suspensory ligament describes any ligament that supports a body part, especially an organ. Types include:* In humans** Suspensory ligament of thyroid gland or Berry's ligament** Suspensory ligament of clitoris...

. This means that anaesthetic in the tarsometatarsal joint can occasionally desensitize pain arising from suspensory ligament, giving the false impression that joint pain has been abolished.

Scintigraphy

Scintigraphy
Scintigraphy
Scintigraphy is a form of diagnostic test used in nuclear medicine, wherein radioisotopes are taken internally, and the emitted radiation is captured by external detectors to form two-dimensional images...

 (bone scan) can help to differentiate between suspensory origin desmitis and bone spavin.

Treatment of bone spavin

Bony changes of the lower hock joint are irreversible. It is possible, however, to manage the problem and thereby slow the progression of the bone spavin, ease the pain, and control the lameness. Surgery is an option for horses that do not respond to conventional treatments.

Medications

NSAIDs, or non-steroidal anti-inflammatory drug
Non-steroidal anti-inflammatory drug
Nonsteroidal anti-inflammatory drugs, usually abbreviated to NSAIDs or NAIDs, but also referred to as nonsteroidal anti-inflammatory agents/analgesics or nonsteroidal Anti-inflammatory medicines , are drugs with analgesic and antipyretic effects and which have, in higher doses, anti-inflammatory...

s, may help improve the lameness in the horse. However, it is important to note that high doses of NSAIDs given over several days can cause kidney damage, as well as ulcer
Peptic ulcer
A peptic ulcer, also known as PUD or peptic ulcer disease, is the most common ulcer of an area of the gastrointestinal tract that is usually acidic and thus extremely painful. It is defined as mucosal erosions equal to or greater than 0.5 cm...

s. NSAIDs may also be illegal in competition, so it may be necessary to stop treatment with NSAIDs several days before the horse competes.

Corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...

 injections
into the lower hock joints may solve the lameness of the horse for several weeks or months. Unlike other joints, the drugs can be repeatedly injected into the lower tarsal joints as needed. Again, it is important to check association rules to see if corticosteroids are not allowed in competition, so that they may be discontinued before the horse competes.

Other joint medications, like hyaluronic acid
Hyaluronan
Hyaluronan is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues...

and Adequan, may help alleviate the pain if the horse has mild bone spavin. However, they are less useful for treating moderate of severe cases. MSM may also help horses with moderate bone spavin.

Shoeing

Proper shoeing is critical in the management of a horse with bone spavin. Shoes most helpful for these horses include shoes that assist in breakover (like a square or rolled toe, or shoes with wedge pads). Shoes with heel support may also help horses with bone spavin, such as egg bar shoes.
A set toe can be applied to protect the toe from increased wear, as lack of flexion in the hock will cause the horse to drag its toe. A trailer or lateral extension can be fitted to prevent an axial swing developed by the horse, allowing the horse to make contact with the ground earlier and prevent rotation within the hock.
Each case of bone spavin should be shod independably depending on the severity of the case and the horses needs, there is not a specific shoe to be applied.

Exercise and work

It is best for a horse with bone spavin to be exercised daily. Preferably, this should be ridden or driven work, as round pen or longeing exercise places uneven stress on the joint. Pasture turnout may not be beneficial if the horse does not move much.

It is best to decrease the intensity of the workload for a horse with bone spavin. However, even with careful management, bone spavin will progressively get worse, and the animal may not be able to continue at the level of competition it was first used for once the lameness is consistent. Many horses can still be successful in a less-strenuous career. Light exercise is better than no exercise at all, and a change of career may prolong the horse's useful life.

Surgery

Fusion of the joint with bone may end the lameness, as the joint has then become stable. However, this may take several years, or never occur. In these cases, surgery may be an option.

Some of the joint cartilage is destroyed with a drill bit or a laser, and the holes are sometimes filled with bone graft
Bone grafting
Bone grafting is a surgical procedure that replaces missing bone in order to repair bone fractures that are extremely complex, pose a significant health risk to the patient, or fail to heal properly....

s.

The veterinarian may also inject a caustic agent into the joint to destroy the cartilage, as opposed to drilling the joint. After the procedure, the horse will be lame for weeks or months, until the joint has fused.

Exercise can help accelerate the fusion of the bones, so the horse may be hand-walked after the injection. NSAIDs are usually given to ease the pain.

Prognosis for bone spavin

The prognosis for bone spavin varies, depending on several factors including:
  • the number of joints involved
  • the severity of the bony changes within these joints
  • how quickly the horse's condition is worsening
  • what the horse is used for


Most horses cannot continue at a high-level of competition for long. However, many horses can continue happily for use as a trail or pleasure horse, or for light work.

Sources

King, Christine, BVSc, MACVSc, and Mansmann, Richard, VDM, PhD. 1997. Equine Lameness. Equine Research, Inc. Pages 839-847.
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